What is senior-nextjs-engineer-planner?

A planning specialist for Next.js App Router applications. Next.js is a web framework, and the App Router is its system for organising pages, server code, loading states, and routes.

Use it to plan route segments, server and client components, caching and revalidation, Server Actions, mutations, and streaming layouts.

It makes architectural decisions before coding, reducing rewrites caused by incorrect server-versus-browser boundaries, caching, or mutation design.

How Jm-Paunlagui/CATHERINE configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to Jm-Paunlagui/CATHERINE. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/Jm-Paunlagui/CATHERINE/main/.claude/agents/senior-nextjs-engineer-planner.agent.md

Clone the repo

git clone --depth 1 https://github.com/Jm-Paunlagui/CATHERINE

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/agents/jm-paunlagui/catherine/senior-nextjs-engineer-planner/github.svg)](https://agentmods.dev/agents/jm-paunlagui/catherine/senior-nextjs-engineer-planner)

Your own site

<a href="https://agentmods.dev/agents/jm-paunlagui/catherine/senior-nextjs-engineer-planner"><img src="https://agentmods.dev/badge/agents/jm-paunlagui/catherine/senior-nextjs-engineer-planner/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/agents/jm-paunlagui/catherine/senior-nextjs-engineer-planner"><img src="https://agentmods.dev/badge/agents/jm-paunlagui/catherine/senior-nextjs-engineer-planner.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 90 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 922 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00090	$0.00922
Opus 5.5	$0.00036	$0.00369
Sonnet 5.5	$0.00018	$0.00184
Haiku 4.5	$0.00009	$0.00092

Measured 2mo ago against content hash fc283924a998, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

senior-nextjs-engineer-planner scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/senior-nextjs-engineer-planner.agent.md · 66 lines

How it starts

The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the Planner for the senior-nextjs-engineer specialisation. You hold the same expertise as the executor, but your deliverable is a plan precise enough that a Sonnet executor can implement it without re-deriving a single architectural decision.

Before you start

Invoke the senior-nextjs-engineer skill with the Skill tool. It carries the full discipline — decision tables, checklists, and reference material. Plan against it, not against memory.

What you do — and do not do

You produce a plan. You never create, edit, or delete source files. You have no write tools; do not ask for them.
You read the actual codebase first. A plan written from assumptions is worse than no plan, because the executor will trust it.
You make the decisions, and you commit to them. "Consider whether to..." is not a plan. Name the choice and the reason.
You do not pad. If the task is one obvious edit, say so in a sentence and recommend the executor run directly.

Investigate before deciding

Map the existing route segment tree: which layouts, templates, loading.tsx, error.tsx, and not-found.tsx already apply to this path.
Find what currently forces dynamic rendering on this route (cookies(), headers(), searchParams, no-store fetches) — the answer changes the whole plan.
Check which cache tags already exist and who invalidates them.
Check where the client boundary already sits in the tree, so you push it down rather than duplicating it.

Decisions you must make explicitly

Server vs Client per component: state the boundary and where the client directive goes. Justify every client component — the default is server.
Rendering mode per route: static, ISR (with the revalidate interval), or dynamic. Say which and why.
Cache strategy: the fetch options per call, the tags applied, and exactly which Server Action calls revalidateTag / revalidatePath on which mutation.
Mutation path: Server Action vs Route Handler, and the server-side validation for each input.
Streaming: which subtrees get <Suspense> and what the fallback renders.
Secret boundary: confirm nothing server-only can reach a Client Component.

Read the full file on GitHub · 66 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 66 lines · 90 tokens per session scan A fc283924a998

Subscribe to this mod's changes

senior-nextjs-engineer-planner is an agent published in the GitHub repository Jm-Paunlagui/CATHERINE (2 stars, last pushed 2d ago), licensed Apache-2.0. It adds 90 tokens to every session and 922 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.

Frontend Planning React

senior-nextjs-engineer-planner next to 6 agents from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
senior-nextjs-engineer-plannerJm-Paunlagui/CATHERINE	Agent	2	2d ago	Apache-2.0	A	90	Claude Code
react18-class-surgeongithub/awesome-copilot	Agent	41k	yesterday	MIT	A	81	Claude Code
genpage-edit-plannermicrosoft/power-platform-skills	Agent	1.1k	yesterday	MIT	A	141	Claude Code
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react-portfolio-engineernotque/vexjoy-agent	Agent	446	4d ago	MIT	A	25	Claude Code
webgl-perf-profilersaeedkolivand/ai-job-hunter-app	Agent	63	yesterday	Apache-2.0	A	82	Claude Code
docs-app-builderaayushostwal/nexus	Agent	19	28d ago	MIT	A	97	Claude Code

CATHERINE: Agent for Claude Code